President Trump announced on Friday that Director of the Office of Management and Budget Mick Mulvaney will be his new White House chief of staff, apparently on a temporary basis.

“I am pleased to announce that Mick Mulvaney, Director of the Office of Management & Budget, will be named Acting White House Chief of Staff, replacing General John Kelly, who has served our Country with distinction,” the president tweeted. “Mick has done an outstanding job while in the Administration… I look forward to working with him in this new capacity as we continue to MAKE AMERICA GREAT AGAIN!”

While Mulvaney was named acting chief of staff, a senior administration official told reporters that there is “no time limit” on his tenure.

“He’s the acting chief of staff, which means he’s the chief of staff. He got picked because the president liked him, they get along,” the official told pool reporters.

Mulvaney will replace current Chief of Staff John Kelly, who is set to exit the White House in January. “John will be staying until the end of the year,” the president added. “He is a GREAT PATRIOT and I want to personally thank him for his service!”

Mulvaney, who once described himself as a “right-wing nutjob,” was selected as Trump’s first budget director after serving four terms in the U.S. House, representing South Carolina’s 5th congressional district.

As a congressman, he was known as a tea-party leader who co-founded the House Freedom Caucus, Congress’ most hardline conservative faction. He endorsed Trump in the 2016 election after initially supporting Sen. Rand Paul (R-KY) during the Republican primaries.

Throughout the general election, Mulvaney often echoed Trump’s rhetoric, especially about Democratic nominee Hillary Clinton. “Some people in our society are just too big to jail,” he lamented in a July 2016 tweet about the former secretary of state. In another tweet, he remarked that “perjury hasn't been a crime for a long, long time” for the Clintons.

As Trump’s budget director, Mulvaney often engaged in conspiratorial rhetoric about his foes, at one point accusing—without a shred of evidence—the Obama administration of having fudged its jobs numbers.

In 2017, Mulvaney dismissed a damning Congressional Budget Office scoring on Republican efforts to repeal and replace the Affordable Care Act by accusing the nonpartisan agency of being partisan and suggesting its health-analysis director was a Hillary Clinton plant.

He also generated controversy by saying Meals on Wheels and other after-school educational programs were “not showing any results” in academic grades when he justified cutting their budgets. “We can’t spend money on programs just because they sound good,” he said.

While heading up the CBO, Mulvaney also served as acting director of the Consumer Financial Protection Bureau up until just this week. Under his leadership, morale at the CFPB reportedly plummeted. He also dismantled the agency’s advisory council, leading to backlash in which critics claimed he only wanted to hear views from “his inner circle.”

In a controversial move, he also stripped the agency’s Office of Fair Lending and Equal Opportunity of its authority—refocusing its mission on “advocacy, coordination, and education” and away from going after discriminatory lenders.

Other candidates for the chief of staff role reportedly included Vice President Mike Pence’s Chief of Staff Nick Ayers, former New Jersey Gov. Chris Christie, Rep. Mark Meadows (R-NC), former Trump deputy campaign manager David Bossie, acting Attorney General Matthew Whitaker, Treasury Secretary Steve Mnuchin, and U.S. Trade Representative Robert Lighthizer.

Christie took himself out of the running in a Friday statement, while Meadows was reportedly asked by the president to remain in Congress, and Ayers announced that he would be leave his White House role by year’s end.

Kelly was sworn in as Trump’s chief of staff in July 2017 and spent more than a year in the role, overseeing a White House reportedly roiled by infighting, a domestic-abuse scandal, and reports of tensions between the president and his top manager.

Kelly’s predecessor Reince Priebus served in the role for a mere six months.